Thyroid Function Evaluation and Management

Essential Tests for Thyroid Dysfunction

When TSH is abnormal, measuring free T4 is necessary to distinguish between subclinical and overt thyroid dysfunction, and considering anti-TPO antibodies is recommended if autoimmune thyroiditis is suspected, according to the Journal for ImmunoTherapy of Cancer 1, 2
The American College of Endocrinology recommends measuring anti-thyroid peroxidase (anti-TPO) antibodies to confirm autoimmune etiology, which predicts 4.3% annual progression to overt hypothyroidism versus 2.6% in antibody-negative patients 2
Measuring lipid panel is reasonable, as subclinical hypothyroidism may affect cholesterol levels and treatment with levothyroxine may lower LDL cholesterol, as suggested by the Endocrine Society 2
Repeating TSH in 3-6 weeks before initiating treatment is recommended, since 30-60% of elevated TSH values normalize spontaneously, according to the American Thyroid Association 2

In patients with suspected central hypothyroidism, free T4 must be measured alongside TSH, as TSH may be inappropriately normal or only mildly elevated despite low fT4, as recommended by the Journal for ImmunoTherapy of Cancer 1, 2
Checking early morning ACTH and cortisol is necessary before starting thyroid hormone replacement, as initiating levothyroxine before corticosteroids can precipitate adrenal crisis in patients with concurrent adrenal insufficiency, according to the Endocrine Society 1, 2
Measuring glucose and HbA1c is recommended, as new-onset diabetes can occur with immunotherapy, as suggested by the Journal for ImmunoTherapy of Cancer 1
In patients on levothyroxine, measuring TSH and free T4 together during dose titration every 6-8 weeks is necessary, as fT4 helps interpret ongoing abnormal TSH levels, according to the American Thyroid Association 2

Measuring TSH, free T4, and thyroglobulin (Tg) is recommended at follow-up visits, as suggested by the American Thyroid Association 3
Measuring thyroglobulin antibodies is necessary simultaneously with Tg, as their presence interferes with Tg measurement, according to the Endocrine Society 3
Target TSH varies by risk stratification: 0.5-2 mIU/L for low-risk patients, 0.1-0.5 mIU/L for intermediate-risk, and <0.1 mIU/L for high-risk or persistent disease, as recommended by the American Thyroid Association 3, 2

Measuring TSH and free T4 is necessary, as inadequate treatment during pregnancy increases risk of preeclampsia, low birth weight, and neurodevelopmental effects, according to the Endocrine Society 2
Target TSH should be maintained in the low-normal range (0.5-2.5 mIU/L) during pregnancy, as recommended by the American College of Obstetricians and Gynecologists 2
Levothyroxine requirements typically increase 25-50% during early pregnancy, necessitating more frequent monitoring, according to the American Thyroid Association 2

Measure anti-TG antibodies simultaneously with TPO antibodies when screening for autoimmune thyroid disease, as approximately 10-20% of patients with Hashimoto's thyroiditis have isolated anti-TG positivity without TPO antibodies 4, 5

Up to 65 % of individuals with superior limbic keratoconjunctivitis have underlying thyroid dysfunction, supporting the recommendation to include thyroid antibody testing in the diagnostic evaluation. 6